Devices and method for access and visualization for lumbar interbody fusion  (lif)

ABSTRACT

A camera and expandable bladed retractor system. The system includes a camera, with a distal-most optical element disposed over the proximal end of the lumen or surgical channel established by the retractor blades. The camera may be fixed to the retractor, either to the proximal end of a blade or to a frame member.

This application is a continuation of U.S. application Ser. No.16/262,543, filed Jan. 30, 2019, pending, which claims priority to U.S.Provisional Application 62/624,021, filed Jan. 30, 2018, expired, andU.S. Provisional Application 62/795,845, filed Jan. 23, 2019, expired.

FIELD OF THE INVENTIONS

The inventions described below relate to the field of spine surgery.

BACKGROUND

Various conditions of the spine, such as herniated discs, arthritis(spondylosis), misalignment of the spine (spondylolisthesis, scoliosisor hyperlordosis/kyphosis) can be treated with minimally invasivesurgery, which is accomplished through narrow channels created andmaintained by expandable bladed retractors. For example, LumbarInterbody Fusion surgery is used to fuse adjacent vertebra, to treat avariety of conditions. The surgery entails removal of a portion of anintervertebral disc, placement of a “cage” or “interbody fusion device”between the discs, and placement of bone graft material between thediscs (and subsequent installation of screws and posts to hold the twovertebrae in place while they fuse together). To gain access to theintervertebral disc in a minimally invasive surgery, a surgeon mayapproach the spine through a retractor system placed in one of severalpathways. The spine may be approached from the side of the patient(lateral lumbar interbody fusion), from the front of the patient(anterior lumbar interbody fusion), obliquely from the front of patient(oblique lumbar interbody fusion), from the back of the patient(posterior or transforamen lumbar interbody fusion), and obliquely fromthe back of the patient (oblique lateral interbody fusion). Especiallyfor the deeper routes (anterior, oblique, and lateral routes), aretractor system with long retractor blades is used, and visualizationis currently obtained through a surgical loop or a surgical microscopeintermittently looking down the passage. These instruments arenecessarily disposed quite a distance from the surgical opening, makingit difficult to view the surgical space, and require a surgeon to lookthrough the loop or microscope, which may require taking on anuncomfortable posture while performing surgery. Visualization through anendoscope has also been proposed, with the endoscope disposed within thechannel established by the retractor blades and extending to the distalend of the blades, near the surgical field. The endoscope takes upvaluable space within the channel, and does not provide a view of tooltips within the channel, and the field of view may be limited if theendoscope is placed close to the surgical field.

SUMMARY

The devices and methods described below provide for improved lateralsurgical access and visualization for minimally invasive lumbarinterbody fusion procedures, to treat conditions of the spine such asherniated discs, arthritis (spondylosis), misalignment of the spine(spondylolisthesis, scoliosis or hyperlordosis/kyphosis). The devicescomprise bladed retractors which include two or more blades which areseparable to retract tissue overlying the spine, and a camera disposedat the proximal end of the retractor. The device can further comprise anoptical assembly including a lens and a prism, disposed on one of theretractor blades, which may be moved along the length of the blade, toobtain a view of a surgical site deep within the body, or an opticalassembly including a lens and a prism, disposed on one of the retractorblades, which may be tilted over the opening of the retractor, to obtaina view of a surgical site deep within the body. The camera assembly mayalso be mounted on a camera boom, attachable to the retractor system,which allows for translation of the camera on 2 or 3 axes relative tothe retractor frame or surgical opening, and/or allows for rotation ofthe camera to align the camera viewing axis with the surgical workspaceat the distal end of the retractor blades. With these features, asurgeon can obtain images of a surgical field deep within the body,through a surgical channel maintained by retractor blades of variableconfiguration, and alter the viewing axis of the camera as necessary toaccount for expansion of the bladed retractor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates typical surgical approaches to the spine, for whichthe retractor may be used.

FIGS. 2, 3 and 4 illustrates a bladed retractor system suitable foraccess to the lumbar spine, fitted with optical elements and aproximally mounted camera.

FIGS. 5 and 6 are proximal views of the bladed retractors system ofFIGS. 2 and 4.

FIG. 7 illustrates a retractor system with splayed blades, with a camerarotatably mounted on the proximal end of a blade.

FIG. 8 shows the retractor system with a camera slidably mounted on aretractor blade.

FIGS. 9 and 10 illustrate an embodiments of the retractor system.

FIGS. 11, 12, 13 and 14 illustrate systems comprising a camera assemblyconfigured for attachment to a bladed retractor, with a mount foradjustably mounting the camera over the surgical opening maintained bythe retractor blades.

FIG. 15 illustrates a system comprising the camera assembly mounted on atable-fixed flex arm, to be used in conjunction with a bladed retractor.

DETAILED DESCRIPTION OF THE INVENTIONS

FIG. 1 illustrates typical surgical approaches to the spine, for whichthe retractor may be used. This illustration shows a coronal crosssection of a patient 1, taken through the midsection at the level of thelower back and lumbar spine. Lumbar Interbody Fusion surgery is used tofuse one vertebra, such as vertebra 2, to an adjacent vertebra, to treata variety of conditions. The surgery entails removal of a portion of anintervertebral disc, placement of a “cage” or “interbody fusion device”between the discs, and placement of bone graft material between thediscs (and subsequent installation of screws and posts to hold the twovertebrae in place while they fuse together). To gain access to theintervertebral disc in a minimally invasive surgery, a surgeon mayapproach the spine through a retractor system 3 placed in one of severalpathways. As shown in FIG. 1, the spine may be approached from the sideof the patient (lateral lumbar interbody fusion), from the front of thepatient (anterior lumbar interbody fusion), obliquely from the front ofpatient (oblique lumbar interbody fusion), from the back of the patient(posterior or transforamen lumbar interbody fusion), and obliquely fromthe back of the patient (oblique lateral interbody fusion). Especiallyfor the deeper routes (anterior, oblique, and lateral routes), aretractor system with long retractor blades is used, and visualization,which is currently obtained through a surgical loop or a surgicalmicroscope intermittently looking down the passage, may instead beobtained with a camera assembly with optical components mounted to oneof the retractor blades or retractor frame arms. Images obtained by thecamera can be displayed on a display screen viewable by the surgeon, andthe surgeon can perform procedures through the retractor while viewingthe procedure on the display. (This system may use multiple cameraassemblies, including a separate camera assembly on each blade.)

As shown in FIGS. 2 through 7, the system includes the retractor 3comprised of several blades 4 depending from a frame 5. Fixationelements 6 (manually operable screws, clamps, or any other manuallyoperable means for fixation) at the proximal end of each blade areinteroperable with the arms 7 of the frame. The frame holds the bladesin rigid but adjustable relationship to each other and the frame opening8, over a surgical opening 9 in the patient, to maintain a surgicalchannel 9C between the blades, providing access to the surgicalworkspace at or beyond the distal end of the retractor blades. Theblades may be provided in many forms. As shown in FIGS. 2 and 4, theblades are half-pipes which, when positioned together make up a completetube, and, when separated, comprise two opposing half-pipes defining andbounding the surgical opening 9 which is the open space suitable forinsertion of tools between the retractor blades to reach tissue at thedistal end of the retractor blades (i.e., a surgical corridor). Theblades may be flat and straight, or flared, instead of the partial pipesshown. The frame may be provided in many forms. The form in FIG. 5 iscommon, and includes one or more ratcheted frame members 10 andcorresponding frame arms 7, with blades 4 fixed to the blade arms. Theframe arms may be moved incrementally along the ratcheted frame membersto move the blades toward or away from each other to retract body tissueoutside the blades, and the blades may be movable along the frame armsto adjust the distance between the blades and the ratcheted framemember. FIG. 4 shows the retractor of FIG. 2 with the blade separated,space along the frame (the frame is shown in FIG. 5). Variousconfigurations of bladed retractors are in use, with various structuresfor adjusting the spacing of the blades. For example, the frame cancomprise a plier-style tool, with jaws set on hinges, as in aTIMBERLINE® retractor or MAXACESS® retractor, where the jaws areequivalent to the arms of a framed retractor, or the frame comprises asystem with arms that slide along straight or curved frame members, suchas the Braun MIASPAS® retractor, the Globus Medical Mars retractor, orthe Medtronic DLIF retractor. The split tube (pair of half pipes) makesup the retractor shown in FIGS. 2 and 4, but any number of blades may beused to make up the split tube. As shown in FIG. 6, a retractor systemcan include a tube retractor with four quarter-pipe segments. (And, asshown in FIG. 10, a retractor system can include a tube retractor withthree blades.)

As shown in FIGS. 2 and 4, a camera assembly (a camera, or the imagesensing and optical components of a camera), are disposed on theproximal end of one of the blades (or on the frame). The camera 11,shown in more detail in FIG. 3, comprises the prism or reflector (or setof mirrors) 12, a lens or lenses 13 (which may include an achromaticlens or other doublet), the imaging device 14 and the control system 15(if provided in the camera component of the system). The camera assemblymay also include a focal length adjustment knob 16 for translating theimaging sensor along the primary imaging axis, relative to the housing.The lens 13 may be part of an optical assembly that includes additionaloptical components (filters, beam splitters, etc.). The imaging device14 may be any suitable image sensor such as a CCD sensor or CMOS sensor.The control system 15 may include a controller, data processingcomponents and transmitters such as a controller and a transmitter andappropriate image processing software to control the camera and transmitdata from the camera (the data output system may be located off thedevice). Suitable cables or wireless transmitters may be used to connectthe camera to a display system and a power supply. The imaging sensor ischaracterized by an imaging plane, and the prism is aligned with theimaging plane to direct light directed parallel to the imaging planetoward the imaging plane. As illustrated, the imaging plane is parallelto the long axis of the assembled blades, and the prism/reflector isdisposed along a line perpendicular to the imaging plane, and isoriented to direct light from the surgical field at the distal end ofthe cannula tube onto the imaging plane.

In the system of FIGS. 2 and 4, all the components of the cameraassembly are disposed proximate the proximal end of the retractorblades, with the distal-most optical component of the camera assembly(such as the distal face of the prism or the distal surface of anobjective lens) proximate the proximal end of the retractor blades, andpreferably proximal to the proximal end of the retractor blades (and,preferably, outside the body of the patient), so that the entirety ofthe camera assembly is located outside the lumen established by theretractor blades and bounded by the distal and proximal ends of theretractor blades.

The arranged retractor blades define the surgical channel and alongitudinal axis 17L which extends through the space defined andbounded by the blades. The imaging sensor has an imaging sensor viewingaxis (a primary viewing axis) 17S, extending at a perpendicular to thesensor surface and intersecting a radially facing surface of the prism.As illustrated, the central longitudinal axis and the imaging sensorviewing axis intersect at about an 85-95° angle. In alternativeconfigurations, the angle is within the range of about 45° to 135°, orwithin the range of about 60° to 120°. The angle may be greater than orless than 90° depending upon the desired configuration and the distancebetween the retractor blades when separated during use.

The prism is characterized by a prism viewing axis 17P (a secondaryviewing axis, which is the line of sight through the cannula, from theprism to the distal end of the cannula) which intersects a distalsurface of the prism, and extends axially distally through the tubularbody toward target tissue. The prism viewing axis preferably intersectsa longitudinal axis of the blade assembly (a central axis, forsymmetrical blade arrangements, or a near central axis for otherconfigurations) near the distal end of the blades, or within about 4 cmor 2 cm or less from the distal end of the cannula. The prism overhangsthe retractor opening by no more than about 25% of the inside diameterof the lumen, generally by no more than about 15% or 10% or less of theinside diameter of the retractor opening (when the blades are closedtogether as shown in FIG. 2), such that it minimally interferes withinstruments passing through the retractor opening. Thus, the prismviewing axis 17P preferably resides at an angle to the centrallongitudinal axis. Depending on the type of prism used, the prismviewing angle may be perpendicular to the distal optical surface of theprism (for a reflective, right angle prism shown in the figures, inwhich the long surface is used as the roof, for example), and the prismmay be disposed over the retractor opening such that the distal opticalsurface is tilted slightly, relative to the transverse plane of theretractor opening, to aim the prism viewing axis at the desired point,such as an intersection with the central longitudinal axis of theretractor opening at the distal end of the cannula. For other reflectiveand deflective prisms for which the viewing angle is not perpendicularto the distal optical surface, the distal optical surface can be angled,as appropriate, to aim the prism viewing axis at the desired point suchas an intersection with the central longitudinal axis of the cannula atthe distal end of the cannula. Various forms of prisms may be used,including a pentaprism, half pentaprism (a non-inverting andnon-reverting prism which bends light 45° from the prism viewing axis,so that the imaging sensor viewing axis may be disposed at about a 45°angle to the prism viewing axis or the cannula longitudinal axis), aSchmidt prism (an inverting and reverting prism which bends light 45°from the prism viewing axis, so that the imaging sensor viewing axis maybe disposed at about a 45° angle to the prism viewing axis or thecentral longitudinal axis), Porro prisms (an inverting and revertingprism which displaces the light entering the prism to an offset butparallel path, so that the imaging sensor viewing axis may be parallelto but radially displaced from to the prism viewing axis or the centrallongitudinal axis) or other prisms, or combinations or configurations ofprisms (and Amici/Penta prism combination, for example, or a right angleprism disposed with the long surface facing distally, so that the rightangle surfaces serve the reflecting surfaces to redirect the image alongan anti-parallel path to the prism viewing axis, optionally paired witha second right angle prism to redirect the image to a parallel butoffset path, or a Bauerfeind prism), operable to reflect or displacelight from the distal end of the cannula toward the imaging sensor.

The central longitudinal axis of the system is variable, depending onhow far apart the blades are positioned. The camera is thus hinged tothe retractor system, either to the frame or to the proximal end of ablade, such that it is rotatable about an axis perpendicular to a longaxis of the surgical channel. The camera may be secured to the systemthrough a hinge, a crescent hinge, a flex hinge or rocker 18, so thatthe camera may be tilted to direct the prism viewing axis to the centerof the surgical field distal to the blades (or elsewhere in the surgicalfield). The camera may be tilted manually by the surgeon, or it may betilted in response to opening of the retractor blades, through linkagesconnecting the camera and hinged to the retractor frame members and theretractor arms. Also, the retractor system may be capable of splayingthe blades, so that the distal tips of the blades are farther apart thanthe proximal end of the blade. This is depicted FIG. 7. With the cameraassembly rotatably mounted on the frame or blade, the camera may berotated to keep the prism viewing axis directed toward the desired pointin the surgical space. This will typically be a point at or near anintersection of the central longitudinal axis at or near the distal endof the blades, or just distal to the distal end of the blades. Therotation of the camera may be accomplished through mechanical linkagesto the frame and blade, or it may be accomplished manually by thesurgeon using the retractor. The rotation may be accomplished graduallyas the retractor blades move from a closed configuration to an openconfiguration and vice-versa, or it may be accomplished step-wise, oronly when re-configuration is complete.

FIG. 8 shows the retractor system with a camera slidably mounted on aretractor blade. With the camera components sized appropriately, thecamera assembly 11 is slidably mounted on the retractor blade throughthe mount 19. This can be accomplished with a clip slidably secured to along edge of a blade, or with a bolt or braking mechanism secured to thecamera assembly and a corresponding channel in a blade, such that thebolt and camera assembly are slidable along the channel. The camera andbolt can be secured in the channel with a friction fit or detents or anyother mechanism that allows a surgeon to manually slide the camera withminimal force yet maintain the position of the camera once set by thesurgeon. The camera is preferably rotatably fixed to the channel,through a hinge or flex hinge, so that it may be rotated or tiltedtoward the center of the surgical field as the camera is movedproximally and distally along the blade, or as the blades are opened orsplayed. Where the camera is quite small relative to the retractoropening, the camera assembly can be provided without a prism orreflector, and the imaging sensor viewing axis can be aimed toward thecenter of surgical field, and the camera can be rotated as describeabove to keep the imaging sensor viewing axis intersecting the centrallongitudinal axis (as described above for keeping the prism viewing axisintersecting the central longitudinal axis) near the distal end of thesystem.

As an alternative to slidably mounting the camera to a blade, the cameraassembly can include an optical pipe or fiber bundle disposed above orbelow the distal face of the prism (such that that distal-most opticalsurface is displaced distally from the imaging sensor), and the entireassembly can be translated distally or proximally along a blade. A prismmay be used both at the distal end of the optical pipe to establish anoptical pathway from the center of surgical field to the light pipe, andat the proximal end of the optical pipe to turn light from the opticalpipe toward the imaging sensor. In each case, the camera assembly, inparticular the distal most optical element (the prism, the tip of thefiber bundle, or a lens at the tip of the fiber bundle) can betranslated longitudinally within the surgical opening. A light sourcecan be added to the camera assembly, or to the inner surface of a blade.The camera assembly is preferably electrically isolated from the blades(if the blades are metallic).

FIG. 9 illustrates an embodiment of the retractor system 20. This systemincludes three blades 21 joined to a frame 22 of fixed proportionsthrough flex hinges. The camera is mounted to the frame via a hinge (acrescent hinge, for example). The frame is fitted with a post 23 whichmay be secured to a mounting arm, which in turn may be fixed to anoperating table used to support the patient during surgery. A number ofLED's 24 are inset in the interior surface of the blades, near thedistal end of the blades, to illuminate the surgical field. FIG. 10illustrates another embodiment of the retractor system 25, with a cameraretrofitted on a plier-type retractor system. This system includes threeblades 21 joined to jaws 26 of an expandable frame, with the cameramounted on the frame near the distal end of one of the blades. In eachcase, the camera may be mounted to the frame via a hinge such that, asthe jaws are opened to enlarge the retractor opening, the camera may berotated or tilted to direct the viewing axis toward the desired area ofthe surgical field at the distal end of the blades.

In use, the cannula blades are positioned in a closed relationship, asclose together as the frame will allow, inserted into a surgical openingin the body of a patient, and then gently pulled open to retract tissueoutside the blade and enlarge the surgical opening. This will provideaccess to tissue deep within the body. In a lateral interbody fusionprocedure, the pathway and corresponding retractor blades are quite long(20 centimeters or so), and it may be quite difficult to see tissue ator beyond the distal end of the retractor. The camera is used to obtainan image of the surgical field, to be displayed on a display screenvisible to the surgeon, so that the surgeon may insert tools through thesurgical opening, going through the surgical channel held open by theretractor blades, and manipulate the tools while viewing the surgicalfield (and at least a portion of the surgical channel) and tools on thedisplay screen. The surgeon may tilt the camera, or slide the cameraalong a blade, as desired to obtain a desired field of view.

The camera assembly and mounting structures can be provided inconfigurations specific to particular retractors, or provided inconfiguration which can fit many retractors of various configurations.For example, the camera assembly may be fixed to an adjustable clamp orspring clip suitable to attachment to the frame, arm, jaw, or blade ofvarious configurations.

FIGS. 11, 12, 13 and 14 illustrate systems comprising a camera assemblyconfigured for attachment to a bladed retractor, with a mount foradjustably mounting the camera assembly over the surgical openingmaintained by the retractor blades. In this system shown in FIG. 11, theretractor comprises the frame 5 including the ratcheted frame members 10and arms 7 mounted on the ratcheted frame members 10, and the blades 4which establish the surgical opening 9. The camera assembly 11 issecured to the retractor system through an articulating camera boom 31,which comprises boom arms necessary to suspend the camera over thesurgical opening 9, with all the components of the camera assemblyproximate the proximal end of the retractor blades, with the distal-mostoptical component of the camera assembly (such as the distal face of theprism or the distal surface of an objective lens) proximate the proximalend of the retractor blades, and preferably proximal to the proximal endof the retractor blades (and, preferably, outside the body of thepatient), so that the entirety of the camera assembly is located outsidethe lumen established by the retractor blades and bounded by the distaland proximal ends of the retractor blades. In this embodiment, thearticulating camera boom comprises a clamp 32 configured for releasableattachment to the frame arm 7, a first boom arm 33 extending away fromthe ratcheted frame member and beyond the blades (relative to theratcheted frame member), and a second boom arm 34 extending inwardlyfrom the first boom arm 33 to a position beyond the tips of the framearms 7. The clamp may be slidably mounted to the frame arm, or the firstboom arm 33 may be slidably connected to the clamp, so that the firstboom arm 33 may be translated along a first axis of the retractor. Thesecond boom arm 34 may be slidably mounted to the first boom arm 33, sothat second boom arm 34 may be translated along a second axis of theretractor. The second boom arm 34 may also be rotatably mounted to thefirst boom arm 33, or the first boom arm may be rotatably mounted on theclamp. The camera assembly is mounted to the second boom arm 34, withthe viewing axis aligned to the surgical opening. The camera isrotatable, relative to the first and second boom arms, about the longaxis of the second boom arm 34, so that the viewing axis maybe tilted asnecessary to point toward the surgical workspace at the distal end ofthe blades. The camera assembly may be rotatably fixed to the secondboom arm 34 through a post 35 rotationally fixed to the camera housingbut rotatably fixed to the second boom arm 34 (the post may fit within abore of the second boom arm 34, or it may be formed as a turret the fitsover a cylindrical portion of the second boom arm 34), or the secondboom arm 34 may be rotatably fixed to the first boom arm 33. The secondboom arm may also be rotatably mounted to the first boom arm, such thatit is rotatable about its long axis, in which case the camera may berotationally fixed to the second boom arm. Also, the camera assembly maybe translatable, toward and away from the first boom arm 33 (whilerotatably held within the second boom arm 34, to position the viewingaxis near the center line C of the retractor frame arms and blades asthey expand. To provide for this translation, the camera may be slidablysecured to the second boom arm 34 through the post, which is, inaddition to being rotatable relative to the second boom arm 34, slidablyfixed within a bore 36 of the second boom arm 34. The boom arms may alsobe rotatably joined, to that the boom arms themselves may be rotated ata hinge point connecting the boom arms.

The configuration illustrated in FIG. 11 provides for positioning thecamera assembly on a variety of existing bladed retractor systems in anobtrusive position, with the blades disposed between the camera assemblyand the retractor frame member 10, and the specific construction can bevaried as needed to fit various retractor systems or to place the camerain different positions relative to the retractor frame components. Onesuch variation is shown in FIG. 12, which uses the same configuration ofthe camera assembly 11 and the post 35 orthogonally fixed to the cameraassembly, with the long axis of the post disposed perpendicular to thesensing axis and/or the viewing axis, and the first boom arm 33 attachedto the retractor frame member 10, between the frame arms 7. Anothervariation is shown in FIG. 13, in which the camera frame 31 consists ofa single boom arm 33, slidably or translatably secured to the ratchetedframe member 10 with a toggle clamp 37, and the camera assembly isslidably mounted to the single boom arm so that it may be translatedtoward and away from the center of the surgical opening. The cameraassembly may also be rotatable about the long axis of the boom arm. Inthis embodiment, the post 35 is disposed on the camera assembly inparallel relationship with the sensor viewing axis (which, in thisembodiment, is perpendicular to the viewing axis of the cameraassembly.)

FIG. 14 illustrates a system in which the camera assembly 11 is securedto the retractor frame through a flexible and malleable member, such asflex arm (also referred to as a gooseneck or a snake clamp) 38. Theflexible and malleable member may be fixed to the retractor 5 at anypoint, and is illustrated secured to the ratcheted frame member 10. Aball joint 39 or hinge can be used to secure the camera assembly to theflexible and malleable member. In this embodiment, the camera assemblycan be disposed about the surgical opening and proximal retractoropening, with its viewing axis aimed at the surgical channel orworkspace, by manipulating the flex arm (and the ball joint, if it isprovided).

FIG. 15 illustrates a system comprising the camera assembly mounted on atable-fixed flex arm, to be used in conjunction with a bladed retractor,to visualize a surgical channel established by the retractor blades orthe surgical field at or near the distal end of the retractor blades.This system includes the camera assembly 11 mounted to the tip oftable-fixed flex arm 41. A mounting tab 42 is fixed to the camera (thecamera may be rotatable upon the tab upper surface, or rotatablerelative to the long axis or transverse axis of the mounting tab) at oneend, and fixed to the end of the flex arm at the other end. The flex armincludes a clamp 43 at one end for secure attachment to an operatingtable 44 or other structure fixed relative to the patient duringsurgery, and a second clamp for secure attachment of the camera assemblyat the other end. A communication cable 45 used to connect the camera toa display system and a power supply can run along the flex arm. With theflex arm secured to the operating table, and the retractor installed ina surgical opening of the patient to establish the surgical channel 9C,a surgeon may position the camera over the surgical opening establishedby the retractor, with the prism viewing axis 17P pointed that thesurgical field at the distal end of the retractor blades, to obtainimages of the surgical field. The camera assembly, including the prismand the distal surface of the prism, are preferably held away from thebody, proximal to (superficial to, or away from the body relative to)the surgical opening 9 and outside the surgical channel 9C. This systemin intended for use in conjunction with a retractor disposed within asurgical opening of a patient, but may be used with any surgical openingwith or without a retractor in the surgical opening.

The retractor systems described above can be used to approach variousstructures in the body, including the lumbar spine as described above,the thoracic spine, the cervical spine through, for example, an anteriorapproach, and various other deep tissues.

While the preferred embodiments of the devices and methods have beendescribed in reference to the environment in which they were developed,they are merely illustrative of the principles of the inventions. Theelements of the various embodiments may be incorporated into each of theother species to obtain the benefits of those elements in combinationwith such other species, and the various beneficial features may beemployed in embodiments alone or in combination with each other. Otherembodiments and configurations may be devised without departing from thespirit of the inventions and the scope of the appended claims.

We claim:
 1. A retractor system comprising: a frame; a plurality ofretractor blades characterized by a distal end and a proximal end, saidretractor blades secured to the frame at their respective proximal ends,said frame operable to move the blades toward a first closely-spacedconfiguration and toward a second widely-spaced configuration, saidretractor blades defining a central longitudinal axis and a proximalretractor opening near the proximal end of the blades, and a distalretractor opening proximate the distal ends of the retractor blades, anda surgical channel extending from said distal retractor opening and saiddistal retractor opening; a camera assembly slidably mounted on theretractor system, and slidable along the length of a retractor bladetoward and away from the distal retractor opening, said camera systemcharacterized by a viewing axis and a distal optical element, saidcamera slidable to align the viewing axis such that the viewing axisintersects the central longitudinal axis near the distal retractoropening when the retractor blades are transitioned between the firstclosely-spaced configuration and the second widely-spaced configuration.2. The retractor system of claim 1, wherein the camera is slidablymounted on the retractor system with a clip slidably secured to a longedge of a retractor blade.
 3. The retractor system of claim 1, whereinthe camera is slidably mounted on the retractor system with a brakingmechanism slidable within a channel in a retractor blade.